The present invention relates to virtual computers, and a CPU allocation method in sharing and operating a plurality of logical CPUs in a time division manner on one physical CPU.
A virtual computer system divides or shares the physical computer resources, such as a CPU, a memory, and an I/O, of a physical computer by a hypervisor, and allocates the divided or shared physical computer resources to a plurality of logical partitions (LPARs), and independently operates an OS on each LPAR, respectively. The OS operating on each LPAR is referred to as a guest OS, and a program operating on the LPAR, including a host program controlled by the guest OS, is referred to as a guest program. On the other hand, the OS operating in a real computer is referred to as a basic OS.
A physical CPU resource allocated to an LPAR is referred to a logical CPU of the LPAR.
The guest OS operates completely similarly to the basic OS in terms of logical operations, but may be inferior in performance as compared with the basic OS due to the characteristics of dividing or sharing the physical computer resources.
On the other hand, the physical computer resource can be effectively utilized by allocating a physical computer resource, which a certain guest OS is currently not using, to other guest OS requiring the physical computer resource.